Dome illuminator for vision system camera and method for using the same

ABSTRACT

This invention provides an illumination assembly that is typically attached to the front end of a vision system camera assembly, adapted to generate an illumination pattern onto an object, which allows the vision system process(or) to perform basic shape inspection of the object in addition to feature detection and decoding. A dome illuminator with a diffuse inner surface is provided to the camera assembly with a sufficient opening side to surround the object. The dome illuminator has two systems to create the pattern on an object, including a diffuse illuminator for specular/shiny object surfaces and a secondary, projecting illuminator for matte/diffusive object surfaces. The diffuse illuminator includes a set of light-filtering structures on its inner surface—for example concentric strips or rings that allow projection of a ringed fringe pattern on an (e.g. shiny/specular) object. The fringes can additionally be generated in a given a certain wavelength and/or visible color.

RELATED APPLICATION

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 16/853,639, entitled OFF-AXIS DUAL-SENSOR VISIONSYSTEM CAMERA AND METHOD FOR USING THE SAME, filed Apr. 20, 2020, whichis a continuation of co-pending U.S. patent application Ser. No.15/859,298, entitled OFF-AXIS DUAL-SENSOR VISION SYSTEM CAMERA ANDMETHOD FOR USING THE SAME, filed Dec. 29, 2017, now U.S. Pat. No.10,628,646, issued Apr. 21, 2020, the teachings of each of whichapplications are expressly incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to machine vision systems for use in finding anddecoding ID codes on objects, and more particularly to cameras for suchvision systems

BACKGROUND OF THE INVENTION

Vision systems that perform measurement, inspection, alignment ofobjects and/or decoding of symbology in the form of machine-readablesymbols (also termed “IDs”, such as a 2D matrix symbol) are used in awide range of applications and industries. These systems are basedaround the use of an image sensor, which acquires images (typicallygrayscale or color, and in one, two or three dimensions) of the subjector object, and processes these acquired images using an on-board orinterconnected vision system processor. The processor generally includesboth processing hardware and non-transitory computer-readable programinstructions that perform one or more vision system processes togenerate a desired output based upon the image's processed information.This image information is typically provided within an array of imagepixels each having various colors and/or intensities. In the example ofan ID reader (also termed herein, a “camera”), the user or automatedprocess acquires an image of an object that is believed to contain oneor more barcodes. The image is processed to identify barcode features,which are then decoded by a decoding process and/or processor obtain theinherent alphanumeric data represented by the code.

In operation, an ID reader typically functions to illuminate the scenecontaining one or more IDs. The illuminated scene is then acquired by animage sensor within the imaging system through optics. The array sensorpixels are exposed, and the electronic value(s) generated for each pixelby the exposure is/are stored in an array of memory cells that can betermed the “image” of the scene. In the context of an ID-readingapplication, the scene includes an object of interest that has one ormore IDs of appropriate dimensions and type. The ID(s) are part of thestored image.

While many applications for ID readers can employ a fixed mountarrangement, with objects moving through an imaged scene, a common typeof ID reader is a handheld arrangement, with or without a “pistol grip”handle. Such readers are used by workers to read IDs on (typically)stationary objects (parts) in a warehouse or other repository. Suchreaders can also be used to identify ID-coded parts in an assembly (e.g.an automobile on a production line), or for any other application thatbenefits from identifying and/or tracking components/parts. In general,working distances, illumination and other parameters for such readerscan vary as a user moves from part-to-part and it is desirable that areader have the capability to handle such variations.

More particularly, to better image ID codes, particularly those on shiny(i.e. reflective or substantially specular) rounded surfaces (e.g.Direct Part Marking, or “DPM” codes), special lighting is desirable.Several approaches have been provided to assist in reading suchcodes—for example, diffusive lighting, low-angle light, polarized lightand/or structured light. This specialized lighting can be used inconjunction with another, conventional illuminator. However, none ofthese approaches has fully addressed two significant challenges inreading (e.g.) DPM codes on round/curvilinear surfaces, namely (a)eliminating the reflection of the reader's camera in the background(a.k.a. the black hole or stripe) when reading DPM codes on shiny,rounded surfaces, and (b) enabling image capture with a plurality ofdiscrete/differing illumination sources simultaneously, so as to improvethe overall acquisition (trigger-to-beep) time.

It is further desirable to provide added data, such as dimensions whenimaging an object to read ID codes. This can be challenging based uponthe surface shape and type—for example matte versus shiny or specularsurfaces.

SUMMARY OF THE INVENTION

This invention overcomes disadvantages of the prior art by providing, anillumination assembly that is typically attached to the front end of avision system camera assembly, adapted to generate an illuminationpattern onto an object, which allows the vision system process(or) toperform basic shape inspection of the object in addition to featuredetection and decoding—for example ID decoding. A dome illuminator witha diffuse inner surface is provided to the camera assembly with asufficient opening side to surround the object. The dome illuminator hastwo systems to create the pattern on an object, including a diffuseilluminator for substantially specular/shiny object surfaces and asecondary, projecting illuminator for matte/diffusive object surfaces.The diffuse illuminator includes a set of light-filtering structures onits inner surface—for example concentric strips or rings that allowprojection of a ringed fringe pattern on an (e.g. shiny/specular)object. As such a single vision system camera arrangement can beemployed to acquire images of any object relatively independent of itssurface properties. From the image of the object with the pattern on it,the shape of the object can be inspected/determined (measured orcompared to a trained reference). The dome illuminator can be tilted toa predetermined angle relative to vertical (for example approximately 15degrees) to avoid the reflection of the camera optics aperture, andallow for identification and resolving of ID code features onshiny/specular object surfaces. The fringes can additionally begenerated in a given a certain wavelength and/or visible color, forexample red, so that when using red light the appearance is of a uniformdiffuse light dome, useful for reading codes, and when using greenlight, the fringes appear dark, and hence a shiny/specular object shapecan be inspected.

In an illustrative embodiment, an illumination system, for a visionsystem camera, which provides image data to a vision system processor,and defines a first optical axis and a field of view (FOV) surroundingthe first optical axis is provided. The illumination system can comprisea dome illuminator having a predetermined length and that substantiallyenvelopes the FOV. The dome illuminator can define an inside emittersurface that is substantially diffuse along at least a portion thereof.The dome illuminator can also approximately define a central axis thatis non-parallel with respect to the first optical axis. As such, thedome illuminator can generate a substantially uniform light distributionon an object in the FOV. A pattern of light-filtering elements canselectively filter light emitted from the inside emitter surface,located along the central axis. The vision system camera can be arrangedto capture an image in the FOV of the pattern of light filteringelements reflected by the object where a surface thereof is shiny. Thevision system processor can be arranged to determine a shape of thesurface of the object based upon the image. Illustratively, the patternof light-filtering elements can define a plurality of stripes thatreside at spaced-apart locations in a direction along the central axisof the inside emitter surface. The pattern of light-filtering elementscan be arranged to define a plurality of approximately concentric ringsabout the central axis within the FOV. The vision system processor cananalyze a geometric arrangement of the concentric rings in the image ofthe object to determine a relative shape of the object. The image caninclude ID code features and the vision system processor can be arrangedto find and decode ID codes in the image. Illustratively, a structuredlight accessory can project structured light so as to define astructured light pattern on an object and the vision system processorcan be arranged to determine a surface shape of the object based uponthe structured light pattern. The vision system processor can bearranged to analyze an object having a non-specular or matte surfacebased upon an arrangement of the structured light pattern on thenon-specular or matte surface and to analyze the object having the shinysurface based upon a diffuse light emitted from the emitter surface.Light sources can be provided in optical communication with the domeilluminator, and can be adapted to project a plurality of discretevisible wavelength ranges through the inside emitter surface. Thelight-filtering elements can be adapted to transmit at least one of theplurality of discrete visible wavelength ranges projected by the lightsources and to filter out another of the plurality of discrete visiblewavelength ranges projected by the light sources. At least one of theplurality of discrete visible wavelength ranges can be projected by thelight sources and the other of the plurality of discrete visiblewavelength ranges projected by the light sources are complementarycolors with respect to each other. The vision system camera can furthercomprise a first imaging system having a first image sensor and firstoptics defining a first optical axis with respect to the FOV. The firstimaging system can be contained in a housing defining a device opticalaxis. The device optical axis can be defined with respect to an aimerbeam or a mechanical geometric reference on the housing. A vision systemhousing can be provided for the system, and adapted for handheld use.The housing can have (a) an aimer illumination source and/or (b) amechanical geometric reference that assists a user in orienting thehousing with respect to features of interest on an object. The visonsystem camera can further comprise a second imaging system having asecond image sensor and a second optics having a second optical axis.The second optical axis can be oriented on-axis with the device opticalaxis adjacent to the FOV. The second optical axis can be broughttogether, on-axis, with the device optical axis by an optical componentthat bends light from a first path to a second path. Also, the firstoptics or the second optics can include an adjustable-focus variablelens, such as a liquid lens.

In another illustrative embodiment, a vision system for imaging anobject can be provided. The vision system can have a first imagingsystem having a first image sensor and first optics defining a firstoptical axis with respect to the object and a vision system processorthat receives image data from the first imaging system. A domeilluminator can be provided, having a predetermined length, arranged soas to substantially envelope the FOV. The dome illuminator can define aninside emitter surface that is substantially diffuse along at least aportion thereof and approximately defining a central axis that isnon-parallel with respect to the first optical axis. As such, the domeilluminator generates a substantially uniform light distribution on anobject in the FOV. A pattern of light-filtering elements can selectivelyfilter light emitted from the inside emitter surface, located along thecentral axis. The vision system camera can be arranged to capture animage in the FOV of the pattern of light filtering elements reflected bythe object where a surface thereof is shiny. The vision system processorcan be arranged to determine a shape of the surface of the object basedupon the image. Illustratively, a structured light accessory can projectstructured light so as to define a structured light pattern on anobject, and the vision system processor can be arranged to determine asurface shape of the object based upon the structured light pattern. Thevison system can comprise a second imaging system having a second imagesensor and a second optics having a second optical axis, the secondoptical axis can be on-axis with a device optical axis adjacent to theobject.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention description below refers to the accompanying drawings, ofwhich:

FIG. 1 is a diagram of a generalized vision system for reading anddecoding features (e.g. Direct Part Marking (DPM) codes) located onshiny/reflective (substantially specular) rounded surfaces, including adiffusive illuminator arranged in an off-axis configuration, accordingto an illustrative embodiment;

FIG. 1A is a diagram of various axes and distances in association withthe vision system configuration of FIG. 1;

FIG. 2 is a diagram of a vision system camera assembly arrangedaccording to the off-axis configuration of FIG. 1, including anintegrated diffuser element on the front end of the camera housing;

FIGS. 3 and 4 are respective diagrams of an exemplary image of a DPMcode on a rounded surface using on-axis and off-axis illumination;

FIG. 5 is a diagram of a vision system camera assembly arrangedaccording to an off-axis configuration, with a further on-axis imagingsystem that views the object through a dichroic mirror located withinthe optical path;

FIG. 6 is a side cross section of an exemplary vision system cameraassembly with a dome illuminator assembly mounted on a front end thereoffor illuminating an exemplary object;

FIG. 7 is a diagram showing an image of an exemplary object having adiffuse light pattern projected by the camera assembly with domeilluminator assembly of FIG. 6;

FIG. 8 is an image of an exemplary object with a shiny, or specular,relatively flat surface showing the layout of fringe patterns producedby light-filtering strips provided on the light diffusing surface of thedome illuminator of FIG. 6;

FIG. 9 is an image of an exemplary object with a shiny, or specular,cylindrical surface showing the layout of fringe patterns produced bylight-filtering strips provided on the light diffusing surface of thedome illuminator of FIG. 6;

FIG. 10 is a side view of a vision system camera arrangement with afrustoconical dome illuminator having a base adapted to tilt thearrangement relative to a supporting surface, according to an exemplaryembodiment;

FIG. 11 is a front oriented perspective view of the vision system cameraarrangement of FIG. 10 showing a set of concentric light-filteringstrips in the dome illuminator that generate a fringe pattern on anobject using light projected by the underlying diffuse surface;

FIG. 12 is a front view of the camera arrangement of FIG. 10 detailingthe layout of the concentric, light-filtering strips around the cameraoptics;

FIG. 13 is an image of an exemplary object having a shiny, or specular,relatively flat surface showing the layout of fringe patterns generatedby the light-filtering concentric strips in the dome illuminator of FIG.10; and

FIG. 14 is an image of an exemplary object having a shiny, or specular,cylindrical surface showing the layout of fringe patterns generated bythe light-filtering concentric strips in the dome illuminator of FIG.10.

DETAILED DESCRIPTION I. Multi-Axis Vision System Camera

FIG. 1 shows a vision system arrangement 100 that is adapted to captureimages and decode features with respect to a shiny (i.e. reflective orsubstantially specular) rounded surface according to an exemplaryembodiment. The system 100 includes a vision system camera assembly 110with a (e.g. two-dimensional (2D)) sensor S and associated lens opticsO. The vision system camera assembly 110 transmits captured images to avision system process(or) 120 that can be instantiated within the cameraassembly entirely, or partially/fully located remote from the cameraassembly—for example in a general-purpose computing device 130, such asa PC, server, laptop, tablet or handheld device (e.g. smartphone). Suchdevice can also be intermittently connected via an appropriate (e.g.wired or wireless) network link 132 for setup and/or runtime control anddata acquisition. Such a device 130 can also include and appropriateuser interface, including a display and/or touchscreen 134, keyboard 136and mouse 138. Acquired data (e.g. decoded IDs) is transferred from theprocessor 120 and/or the device 130 to a utilization device orprocess(or) 140, which can include tracking and/or logistics software orother data-handling/storage applications.

The vision system process(or) 120 can include various functionalprocessor and associated processes or modules. By way of non-limitingexample, such processes/modules can include a plurality of vision tools122, including edge-finders, blob analyzers, calipers, patternrecognition tools, etc. Vision system tools are commercially availablefrom a variety of vendors, such as Cognex Corporation, of Natick, Mass.The process(or) 120 can also include an ID (or other feature) finder anddecoder 124, that uses information retrieved by the vision tools fromacquired images to locate ID candidates (e.g. DPM codes) and decodesuccessfully identified candidates to extract alphanumeric (and other)information. The processor can also include various camera controlprocessor and associated processes/modules, including a trigger and anillumination process(or) 126. This is used to control image acquisitionand operation of the illumination system that projects appropriate lightonto the surface of an imaged object 150.

The depicted object 150 defines a rounded or round (e.g. cylindrical)surface 152, such as a motor shaft or gear stem. By way of example, thesurface can be metallic, and moderately or highly smooth, which rendersit relatively shiny/reflective. This reflectivity can be challengingwhen attempting to acquire a useable image of a future set (e.g. a DPMcode) 154 formed on the surface 152. As shown, the exemplary features154 reside within the field of view FOV of the camera assembly 110,which is defined around an optical axis OA. The FOV is highly variabledepending upon the type of optics employed and the focal distance. Notethat the optics O in this exemplary depiction is arranged in astraight-line configuration. In this depiction the axis OA perpendicularto the image plane of the sensor S and the image of the camera maygenerally appear in the background of the acquired image, which is oftenundesirable. A useable/decodable image of the ID code 154 (with adiffuse background) can be acquired in this configuration when the codeis off-axis. In this case, the center 170 of the cylindrical object 150should be located outside that portion of the field of view (withinboundaries 183) where the code 154 is located.

However, in operative embodiments, it is contemplated that optics can bearranged at a non-perpendicular angle with respect to the sensor—forexample, defining a Scheimpflug configuration, which can allow forextension of the overall depth of field (DOF) and/or avoid a returnedreflection from the camera. Such an arrangement is shown and describedin commonly assigned U.S. patent application Ser. No. 15/844,448,entitled DUAL-IMAGING VISION SYSTEM CAMERA AND METHOD FOR USING THESAME, filed Dec. 15, 2017, the teachings of which are incorporatedherein by reference as useful background information.

Notably, system 100 includes a diffusive illuminator 160, which isadapted particularly to illuminate rounded/curvilinear surfaces, such asthe object surface 152. The position and size of the illuminator 160 areeach accentuated in the depiction of FIG. 1 for the purposes ofillustration and clarity. In various embodiments, the diffusiveilluminator can be integrated with the front end of the camera assembly.The diffusive illumination is projected into the field of view (FOV) bythe illuminator so that it strikes the surface 152 at a range of angles.This creates a lighting effect that accentuates the DPM code around thecurved surface. Such diffusive illumination can be generated bydifferent types of techniques. The diffuser element 162 can be astandard opal diffuser with LED sources (shown as light source I) thatcreate a uniform luminance surface. The diffusive illuminator can alsobe a backlighted/side-lighted film, or an electroluminescent foil. Thegeometry of the diffusive illuminator 160 can be defined as the insidesurface of a dome or semi-cylinder (as shown). The depicteddome/semi-cylinder configuration thereby projects a light that isdesirable for illuminating shiny cylindrical objects and surfaces.Reference is also made to the simplified diagram of FIG. 1A, whichincludes a laser aimer 184, placed aside the camera 110 and associatedaimer beam DOA, which also serves as the “device optical axis”. In theabove-described configuration, the working distance WD from the cameraassembly 110 to the object surface 150 is typically defined by thecrossing of the camera optical axis OA and the illumination diffuser'saxis OAI at the point 186. Note that the diffuser's axis OAI can be arelative axis of symmetry or center of curvature for the concave ordomed surface of the diffuser element, and is shown centered (equalangles β) between the adjacent boundary edge (ray 180) of the camera FOVand the outermost boundary edge (ray 182) of the diffusive illuminator160, and is more generally tilted at a non-perpendicular and non-zero(e.g. acute) angle α. More generally, the device optical axis DOA can bedefined by the aimer beam (as shown), or by mechanical features on thevision system housing. Thus, in operating the handheld implementation ofthe system and method herein, the user directs the aimer beam onto (orin the general region of) the ID code of interest, with the surface ofthe object approximately perpendicular to the aimer beam (and/orperpendicular to a tangent line/plane of the surface at the point of thecode). Note that the mechanical features on the vision system housingthat define the Device Optical Axis can include (for example) (a)visible lines on the outside of the housing, (b) the parting linebetween the parts of the enclosure (where the housing enclosure isformed in halves that are fastened or adhered together during assembly),and/or (c) a flat surface or window on the front side of the housing(i.e. on its code-reading end), recognizing that users can (usually)successfully position a device with a flat front surface or windowparallel to the object surface. In such case the direction perpendicularto the front surface of the housing can be considered as the deviceoptical axis. The device optical axis is defined as the preferredreading direction and location, in other words, the reading performanceis optimized if the code is on or near the device optical axis and thesurface of the object is perpendicular to the device optical axis.

As also depicted in FIG. 1, the location of the feature of interest(e.g. an ID code 154 (FIG. 1)) on the object 150 is at the point 186where axes OA, OAI and DOA intersect. The relationship of this point 186to the partial field of view 183, the surface 152 of the object 150 andthe object center 170 is also defined by depicted dashed lines 190 and192.

Note that the arrangement of the diffuser's optical axis OAI versuscamera optical axis OA is termed “off-axis” in that the illumination isaligned at a non-zero angle with respect to the camera optical axis.This varies from an on-axis illumination arrangement, in whichillumination is directed at a zero angle (i.e. aligned with) the cameraoptical axis. Note further that the camera assembly 110 can include aconventional (e.g. on-axis) illumination system that directsillumination in a straight line toward the object along the optical axisOA—for example, a set of high-powered LEDs AI arranged around theperimeter of the optics O. An appropriate cover, diffuser and/or filtercan be provided over the LEDs—also described below. The LEDs AI can bepart of a low-angle-light illumination system that supplements thediffusive illumination. Alternatively, a separate low-angle system canbe located on a mounting that is either attached to, or remote from, thesystem device housing.

Further reference is made to FIG. 2, which shows a vision systemarrangement 200, including a camera assembly 210 for reading anddecoding ID features provided in the above-described off-axisconfiguration. This camera assembly can include an on-board visionsystem processor and associated ID-decoding functional module. Thecamera assembly 210 also includes an attached/integrated diffusiveilluminator 220. The diffuser element or emitter 222 is arranged toprovide sufficient coverage on the object surface to illuminate theadjacent background, and hence the ID code features are effectivelycontrasted—since the projected illumination light 224 arrives at theobject from a range of directions based upon the concave geometry of thediffuser element 222. That is, the refractive effect of the diffuserelement material, combined with the overall geometry thereof, generatesa multidirectional projection of light rays onto each point of theexposed object surface, thus ensuring that the code's features are fullyilluminated regardless of the angle about the object circumference atwhich they occur.

The degree of outward extension and/or radius of curvature of thediffuser element/emitter 222 can vary depending, at least in part, uponthe rounded shiny object's radius/curvature, and the ID code size, andthese parameters define the above-described angle β that is used todesign the diffuser (in which β is located around the diffuser's axisOAI1).

The camera assembly 210 as shown includes a main housing 240 and a frontend 250 that surrounds the optics 230. The illumination assembly (AIabove) can be directed from the front end 250 into the diffuser element222, with the front end component 250 acting as a light pipe. Thecombined front end 250 and diffuser assembly 222 can be integrated intoa single attachment that can be removably applied to a universal camerahousing (240) with associated, integral illumination AI. It should beclear that this depicted arrangement is exemplary of a variety ofassemblies that tie the diffuser element and camera housing together,and provide light to the diffuser element. As described above, inalternate embodiments, the diffuser element is electrically tied to thehousing and includes its own embedded illumination source(s).

The illumination assembly can include an aimer (see the embodiment ofFIG. 5 below) used in conjunction with a handheld version of the system.The aimer projects a structured light beam (e.g. a dot, cross or line)of an appropriate wavelength and/or visible color onto the objectsurface so as to guide the user in properly orienting the system devicewith respect to the object and features of interest (e.g. code).Alternatively, another form of geometrical reference or structure—forexample a sighting assembly, printed indicia with instructions on properorientation and/or a screen with feedback information as to whether thedevice is properly oriented—can be used to assist a user in orientingthe handheld system device.

FIGS. 3 and 4 respectively depict images 300 and 400 of an exemplary(e.g. DPM) ID code 320, 420 on a rounded surface (e.g. a cylindricalshaft) 310, 410. The left image 300 is acquired using a conventionalon-axis illuminator in association with a vision system camera assembly.The image of the code 320 includes a shadow line 350 that obscuresdetails in the code 320, rendering it unreadable (per the indicator360). Conversely, using an off-axis illumination arrangement as shown inFIGS. 1 and 2, the right image 400 contains no obscuring shadows orother occlusions in the same region 450, or elsewhere within the imagedobject surface. In general, the non-zero angle defined between theoverall device optical axis and the optics' optical axis in the off-axisimaging system causes any shadow or footprint of the imaging system tobe located is outside of the imaged code 420. Thus, the code 420 isfully readable per the indicator 460. Hence, the off-axis configurationprovides a significant advantage in reading feature sets/ID codes onrounded objects.

II. Alternate Arrangement

In another embodiment, the overall vision system arrangement can includean additional on-axis imaging system that is adapted to provide a secondset of image data to the overall vision system, acquired with adifferent illumination profile. With reference to FIG. 5, a dual-imagesystem arrangement 500 includes a camera assembly 510 with associatedhousing 520 that can be universal. The front end 550 can include anintegrated (curved, concave, etc.) diffuser element 530 as describedgenerally herein, which receives light from the housing 520 andtransmits the light 532 in a diffuse form toward the object. Thediffuser element 530 defines an axis OA12 that is arranged at a non-zero(e.g. acute) angle α with respect to the camera optics 540 optical axisOA2.

The front end 550 (or another structure associated with the housing 520)can be adapted to support the second imaging system 560 using anappropriate bracket 552 (shown in phantom), or other member. Thison-axis system 560 can be combined in a compact manner with the camerahousing 520 using (e.g.) a dichroic filter/mirror 570 placed in front ofa portion (upper portion as shown) of the diffuser element 530. Theplane of the filter/mirror 570 defines, generally, a 45-degree angle AMwith respect to axis OA12. More particularly, the on-axis system 560 caninclude an on-axis illumination assembly (e.g. LEDs AI1), which can beimplemented (e.g.) as polarized illumination using appropriate filters,etc. The light emitted by the diffusive illuminator can be crosspolarized with respect to the on-axis light so that it can bedistinguished from the on-axis light. The illumination is, thus,projected along the axis OAO of the optics 562 of the system 560.Illustratively, the wavelength of the on-axis illumination and thediffuse illumination are differentiated from each other by a sufficientdegree to allow one of them to be discriminated and attenuated by thedichroic filter 570. The filter 570 is located above the optical axisOA2 of the off-axis camera assembly optics 540 so as to not interferewith image formation therein. The filter 570 allows passage of light 532from the off-axis diffuser element 530, covering all, or a substantialportion thereof. However, the filter 570 is adapted to reflect on-axisillumination (AI1) light received from the object back to the on-axisoptics 562. Likewise, on-axis illumination light is reflected onto theobject by the filter 570 as shown (with the axis OAO bent at a90-degree/perpendicular angle 572). Note that a dichroic filter is oneof a variety of optical components that can generate a desiredlight-bending and aligning effect with the two light paths (for each ofthe imaging systems). In alternate embodiments a beam splitter can beemployed, and/or a variety of other arrangements of prisms, mirrors andfilters, which should be clear to those of skill.

Illustratively, both the off-axis and on-axis imaging systems/cameras510 and 560 can include a respective focusing system, such a variable(e.g. liquid) lens, which is provided with respect to the optics 540 and562. In an embodiment, the off axis system 510 can include a predestinedworking range in which features are imaged from objects, while theon-axis system can be adapted to image at an indefinite range, so thatthe overall reading distance of the combined arrangement 500 isextended.

Notably, the on-axis illumination AI1) can function as an aimer, inparticular delimiting the field of view of the overall arrangement 500,or the aimer can also be a dedicated light source that defines thedevice optical axis to guide the user to properly orient the arrangement500. It is contemplated that the arrangement 500 can be orientedproperly using other mechanisms and functions, such as a sightingsystem, a grip assembly, etc.

The vision system processor 580—which can reside fully or partiallywithin the arrangement's housing 520, or within a remote device (e.g.PC, laptop, tablet, handheld, etc.), is adapted to handle image datafrom each imaging system/camera 510 and 560. This data can be combined,or otherwise compared, using and appropriate process(or) 582. Imageacquisition of data from each imaging system 510, 562 can be sequentialor concurrent. Notably, an advantage to the use of a dichroic filter isthe ability to acquire images from both systems concurrently, and notsequentially. This saves time in the acquisition process. That is, thereceived light from the first image system's illuminator (firstwavelength) only passes to the first imaging system and received lightfrom the second imaging system's illuminator (second wavelength) onlypasses to the second imaging system—based upon the differentiatingfunction of the filter. Operation of each illuminator (eithersequentially or concurrently) is controlled by the illuminationprocess(or) 586. Additionally, the focus of each imaging system's 510,560 variable optics 550, 562 is controlled by the focus process(or) 586.Note that one or both of the optics can be fixed in alternateembodiments.

The results 590 that are provided by the arrangement 500 can be based ona successful reading of object features/IDs from either the off-axis oron-axis imaging system. The results can also be based on a combinationof features from the two imaging systems, forming a composite imageusing techniques known to those of skill. In an embodiment, theprocess(or) 580 can employ a technique that first attempts to decodeeach image, and then if no successful result is generated from thediscrete images, it combines these images and attempts to decode thecomposite image. Other techniques can be used to employ one or bothimaging systems in alternate embodiments to achieve successful readingof features.

It should be clear that the above-described system for illuminatinground object surfaces, using an off-axis curved diffuser elementprovides a more uniform lighting effect, and improved identification offeatures, such as ID codes. The system can provide enhanced range andversatility by incorporating an additional imaging system with anon-axis illuminator, which can also act as an aimer.

III. Dome Illuminator for Vision System Camera

It is contemplated that the use of structured light and other forms ofadvanced illumination/illuminators can allow for the use of theabove-described multi-axis camera arrangement in other types of visionsystem applications, including inspection and robot control, in additionto ID code reading. Thus, it is contemplated that generalizeddimensioning capabilities can be provided to the vision system throughuse of a dome illuminator assembly. With reference to FIG. 6, a visionsystem camera arrangement 600 is shown. The camera 600 (shown in crosssection) can be based upon the above-incorporated multi-axis U.S. patentapplication Ser. No. 15/844,448. In general, the camera 600 can includea main housing 610 with processing boards 612 and 614, whichinterconnect to an image sensor circuit board 616 and associated 2Dsensor 617. An optics package 618 is provided at the front end of thecamera. The constituent components (lenses, filters, etc.) of the opticspackage 618 can vary based upon the task, and typically includes aplurality (stack) of lenses, including one or more variable (e.g.liquid) lens(es) 622 that provide adjustable focus, depth of field (DOF)etc., based upon commands of the vision system processor (including, butnot limited to, processing boards 612 and 614). As described in theabove-incorporated U.S. patent application, the optics 618 defines anoptical axis 620 that is aligned (i.e. is on-axis) with respect to anaxis perpendicular to the plane defined by the image sensor 617. Thefront end 620 of the camera assembly 600 includes various illuminationsources, and can optionally include additional lenses and mirrors thatprovide a second optical path that is off-axis (i.e. not aligned with,and at an angle to the primary optical axis 620, and that transmitslight from the imaged scene to a second image sensor, or to a portion ofthe main image sensor 617.

The camera arrangement 600 includes a dome illumination assembly (alsotermed a “dome illuminator”) 640, which is shown mounted forward of thecamera front end 620 in a manner that provides clearance for the fieldof view 630 of the optics 618. The dome illuminator 640 operates togenerate a uniform background illumination so that features, such as IDcodes, can be identified and distinguished of objects 650 havingspecular (reflective/shiny) surfaces. The dome illuminator 640 transmitslight via a diffusing light pipe 642 that fully surrounds the object650. The light pipe 642 can be constructed from any translucentacceptable material, such as polyethylene, acrylic or polycarbonate. Thelight transmitted by the pipe is generated by sources 644 residing inthe front end 620 of the camera 600 in the exemplary embodiment, but canbe provided by sources directly integrated, or attached to, the domeilluminator in alternate embodiments. The dome illuminator can projectlight in a given wavelength range—for example green, visible red,near-infrared (IR), IR or ultraviolet (UV)—so that the sensor 617 and/orfilters in the optics 618 can differentiate the light of the domeilluminator from other light sources.

Note also that the dome illuminator 640, and the associated optical axis620, is tilted with respect to the object (and/or its supporting surface652) at an angle AD relative to the perpendicular 654. This arrangementis described further below. By way of non-limiting example, the angle ADcan be approximately 15 degrees. The angle AD is highly variable—forexample, plus or minus 10 degrees or more.

As depicted, a secondary light source 660 can be attached to, and/orintegrated with, the dome illuminator 640 along a side thereof. Thesecondary light source 660 defines an axis 664 that is tilted at anangle DIA with respect to the optical axis 620. The angle DIA is highlyvariable—for example between 10 and 30 degrees. The secondary lightsource 660 is responsive to the vision system processor, or anothercontroller, and define (e.g.) a laser diode or other narrow-bandwidththe/coherent light generator that projects light in a discrete band thatcan be discrete from the wavelength(s) projected through the domeilluminator 640. The secondary light source 660 can include an opticspackage 662 that generates a structured light pattern (e.g. crossinglines as shown on the object 650), so as to define reference features onthe object surface. These reference features thereby provide a patternon the object that can be imaged by the camera in a manner that allowsthe vision system processor to derive basic 2D and 3D measurements ofthe object surface. In this manner, the illuminator can facilitate tasksin addition to ID decoding.

However, it is recognized that a shiny/specular surface will reflectstructured illumination patterns in a manner that obscures the featuressought to be measured by the vision system. This is illustrated by theimage 700 of FIG. 7, in which an exemplary object 710 with anon-specular surface clearly reflects structured line features, while anexemplary object 720 with a shiny/specular surface obscures the linefeatures in a manner that prevents identification by the vision system.The exemplary embodiment addresses this issue by providing a patternedstructure that effectively obscures and/or filters part of the lightprojected from the diffuse surface of the dome illuminator light pipe642. More particularly, a plurality of filtering strips 670 coverportions of the light pipe's diffuse inner surface in the manner ofconcentric rings. In this manner, the diffuse surface of the light pipeprojects light onto the object surface through gaps 672 between strips670. Since the dome illuminator substantially encloses the object, iteffectively isolates the object from ambient light in the surroundingenvironment. Thus, the strips 670 produce a striped effect or pattern(termed also “fringes”) on the object surface. This is shown in FIGS. 8and 9. In particular the exemplary object image 800 in FIG. 8 includesan illuminated (potentially specular) object surface 810 that isrelatively flat, and thus, the darker fringe pattern 820 appears asspread-out rings between the illuminated regions. This pattern layoutthereby provides visual references to the 3D (i.e. z-axis height)topography of the object within a 2D image. One or more ID codes aredepicted (code 830 being bounded by an identifying box), and thus theillumination from the dome illuminator also effectively resolves appliedID codes. In FIG. 9, the exemplary image 900 has also been illuminatedby the dome illuminator with fringe pattern. The surface 910 defines acylindrical topography that results in closely spaced, dark rings 920along the curved dimension. These rings 920 are elongated along theaxial direction (double arrow 924) of the cylinder surface 910. Hencethe vision system, with trained knowledge of the geometry of theprojected fringe pattern, can determine the 3D layout (often considereda 2.5D inspection of the object) of the surface 910. The illuminationalso highlights the features of an ID code 930 applied to the surface910. As shown, the vision system has formed a bounding box 932 aroundthe identified code 930.

More particularly, the known pattern formed on the inner surface of thedome illuminator's diffuse light pipe is reflected from the objectsurface in a manner that provides information on (e.g.) the cylinderradius, flatness of a part or even absence/presence of subparts. This iscombined with the above-described structure light (e.g. laser)projection system in the secondary light source to ensure that bothspecular objects and those with reduced specularity can adequatelyreflect the associated pattern with enough optical quality to ensurethat the vision system can successfully complete an object inspection(e.g. dimensioning, feature-finding, etc.) task.

In operation, the vision system processor can be adapted to operate eachform of illumination in sequence and/or together so that images of theobject can be acquired with specific forms of illumination. Likewise,while the strips that create the fringe pattern can be opaque(non-transmissive) of transmitted light from the diffuse light pipesurface, they can filter light of certain discrete wavelengths inalternate embodiment. For example, the strips can allow green light topass but block red light, and the sensor can be adapted to identifyparticular wavelengths of light at predetermined times. Hence the term“filter” as applied to the fringe-pattern-creating structures (strips)should be taken broadly to include blocking of all transmitted lightwavelengths and/or selective blocking of only some wavelengths, whileallowing others to pass.

FIGS. 10-12 show a vision system arrangement 1000 with a camera assembly1010 and attached done illuminator 1020, according to another exemplaryembodiment. The vision system 1000 defines a longitudinal (cameraoptical) axis 1024 that is tilted with respect to vertical(perpendicular to the ground surface) 1030 by an angle 1032 of (e.g.)approximately 15 degrees. The base/bottom 1040 of the illuminator 1020can be arranged to reside on a flat surface while maintaining this tiltangle. The exterior surface of the illuminator 1020 can be opaque, whilethe inner surface 1110 defines a diffuse light pipe (FIGS. 11 and 12).The light sources can be contained within the camera body or within thestructure of the illuminator 1020.

The shape and dimensions of the illuminator 1020 can vary based upon theapplication and or side of objects being imaged. In an exemplaryembodiment, the inside dimension of the illuminator 1020 defines afrustoconical shape with an overall length 1050 (FIG. 10) and maximum(opening) diameter 1150 (FIG. 11), which can vary both based upon thetask and the steepness of the conical shape. In other embodiments, theinner surface can be a tapered curvilinear surface. The inner surfacecross section (on a plane perpendicular to the axis 1024) can becircular, as shown, polygonal, or a combination of polygonal and curvedshapes.

In this embodiment, with reference to FIGS. 11 and 12, the fringepattern generating strips 1160 define a plurality of decreasing diameterconcentric circles that are applied to the inner diffusive surface 1110of the light pipe. The strips can be constructed from any acceptabletransmissive or translucent material to produce a filtering effect, asdescribed above. In various embodiments, the strips can be moldedunitarily with the material of the light pipe, integral or applied as aseparate structure. In this embodiment, the strips are an assembly witha pair of opposing spacer ribs 1162. The width of the concentric strips1160 are highly variable. The strips 1160 are sized and arranged withinthe interior of the dome illuminator 1020 to produce an appropriatepattern on the object, which allows the vision system to determinerelative contours from an acquired image. While not shown, an off-axis,secondary illuminator can be mounted on or within the housing of thedome illuminator 1020 and project an appropriate structured lightpattern on the imaged object at a predetermined time.

FIGS. 13 and 14 depict respective images 1300 and 1400 of exemplaryspecular objects with the camera assembly 1010 and dome illuminator1020. The image 1300 in FIG. 13 depicts a relatively planar object1310—evidenced by a semicircle of dark fringes 1320. The edge 1330 ofthe object 1310 defines a sharp drop-off where the fringes terminate.Alternatively, the image 1400 of FIG. 14 shows a set of closely spaced,elongated fringes, indicative of a cylindrical object surface. An IDcode 1430 is clearly resolved in the image using the illuminator 1120.

IV. Conclusion

It should be clear that the camera and illumination assemblies describedherein allow for accurate imaging of a variety of object shapes andsurfaces. The arrangements effectively resolve ID codes and otherfeatures and allow for additional tasks, such as dimensioning to beperformed by an associated vision system process(or).

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments of the apparatus and method of the presentinvention, what has been described herein is merely illustrative of theapplication of the principles of the present invention. For example, asused herein, various directional and orientational terms (andgrammatical variations thereof) such as “vertical”, “horizontal”, “up”,“down”, “bottom”, “top”, “side”, “front”, “rear”, “left”, “right”,“forward”, “rearward”, and the like, are used only as relativeconventions and not as absolute orientations with respect to a fixedcoordinate system, such as the acting direction of gravity.Additionally, where the term “substantially” or “approximately” isemployed with respect to a given measurement, value or characteristic,it refers to a quantity that is within a normal operating range toachieve desired results, but that includes some variability due toinherent inaccuracy and error within the allowed tolerances (e.g. 1-2%)of the system. Note also, as used herein the terms “process” and/or“processor” should be taken broadly to include a variety of electronichardware and/or software based functions and components. Moreover, adepicted process or processor can be combined with other processesand/or processors or divided into various sub-processes or processors.Such sub-processes and/or sub-processors can be variously combinedaccording to embodiments herein. Likewise, it is expressly contemplatedthat any function, process and/or processor herein can be implementedusing electronic hardware, software consisting of a non-transitorycomputer-readable medium of program instructions, or a combination ofhardware and software. Accordingly, this description is meant to betaken only by way of example, and not to otherwise limit the scope ofthis invention.

What is claimed is:
 1. An illumination system for a vision systemcamera, that provides image data to a vision system processor, defininga first optical axis and a field of view (FOV) surrounding the firstoptical axis comprising: a dome illuminator having a predeterminedlength and that substantially envelopes the FOV, the dome illuminatordefining an inside emitter surface that is substantially diffuse alongat least a portion thereof and approximately defining a central axisthat is non-parallel with respect to the first optical axis, wherein thedome illuminator generates a substantially uniform light distribution onan object in the FOV; a pattern of light-filtering elements thatselectively filter light emitted from the inside emitter surface,located along the central axis, wherein the vision system camera isarranged to capture an image in the FOV of the pattern of lightfiltering elements reflected by an object having a surface that isshiny; and the vision system processor being arranged to determine ashape of the surface of the object based upon the image.
 2. Theillumination system as set forth in claim 1 wherein the pattern oflight-filtering elements define a plurality of stripes that reside atspaced-apart locations in a direction along the central axis of theinside emitter surface.
 3. The illumination system as set forth in claim2 wherein the pattern of light-filtering elements are arranged to definea plurality of approximately concentric rings about the central axiswithin the FOV.
 4. The illumination system as set forth in claim 3,wherein the vision system processor analyzes a geometric arrangement ofthe concentric rings in the image of the object to determine a relativeshape of the object.
 5. The illumination system as set forth in claim 4wherein the image includes ID code features and the vision systemprocessor is arranged to find and decode ID codes in the image.
 6. Theillumination system as set forth in claim 1, further comprising, astructured light accessory that projects structured light so as todefine a structured light pattern on an object and the vision systemprocessor is arranged to determine a surface shape of the object basedupon the structured light pattern.
 7. The illumination assembly as setforth in claim 6 wherein the vision system processor is arranged toanalyze an object having a non-specular or matte surface based upon anarrangement of the structured light pattern on the non-specular or mattesurface and to analyze the object having the shiny surface based upon adiffuse light emitted from the emitter surface.
 8. The illuminationsystem as set forth in claim 1, further comprising, light sources inoptical communication with the dome illuminator adapted to project aplurality of discrete visible wavelength ranges through the insideemitter surface.
 9. The illumination system as set forth in claim 8wherein the light-filtering elements are adapted to transmit at leastone of the plurality of discrete visible wavelength ranges projected bythe light sources and to filter out another of the plurality of discretevisible wavelength ranges projected by the light sources.
 10. Theillumination system as set forth in claim 9 wherein the at least one ofthe plurality of discrete visible wavelength ranges projected by thelight sources and the other of the plurality of discrete visiblewavelength ranges projected by the light sources are complementarycolors with respect to each other.
 11. The illumination system as setforth in claim 1 wherein the vision system camera further comprises afirst imaging system having a first image sensor and first opticsdefining a first optical axis with respect to the FOV, and wherein thefirst imaging system is contained in a housing defining a device opticalaxis.
 12. The illumination system as set forth in claim 11 wherein thedevice optical axis is defined with respect to an aimer beam or amechanical geometric reference on the housing.
 13. The illuminationsystem as set forth the in claim 12, further comprising a vision systemhousing adapted for handheld use, and at least one of (a) an aimerillumination source and (b) a mechanical geometric reference thatassists a user in orienting the housing with respect to features ofinterest on an object.
 14. The illumination system as set forth in claim11 wherein the vison system camera further comprises a second imagingsystem having a second image sensor and a second optics having a secondoptical axis, the second optical axis being on-axis with the deviceoptical axis adjacent to the FOV.
 15. The illumination system as setforth in claim 14 wherein the second optical axis is brought together,on-axis, with the device optical axis by an optical component that bendslight from a first path to a second path.
 16. The illumination system asset forth in claim 14 wherein the first optics or the second opticsincludes an adjustable-focus variable lens.
 17. A vision system forimaging an object comprising: (a) a first imaging system having a firstimage sensor and first optics defining a first optical axis with respectto the object; (b) a vision system processor receiving image data fromthe first imaging system; (c) a dome illuminator having a predeterminedlength and that substantially envelopes the FOV, the dome illuminatordefining an inside emitter surface that is substantially diffuse alongat least a portion thereof and approximately defining a central axisthat is non-parallel with respect to the first optical axis, wherein thedome illuminator generates a substantially uniform light distribution onan object in the FOV; (d) a pattern of light-filtering elements thatselectively filter light emitted from the inside emitter surface,located along the central axis, wherein the vision system camera isarranged to capture an image in the FOV of the pattern of lightfiltering elements reflected by the object where a surface thereof isshiny; and (e) the vision system processor being arranged to determine ashape of the surface of the object based upon the image.
 18. The visionsystem as set forth in claim 17, further comprising, a structured lightaccessory that projects structured light so as to define a structuredlight pattern on an object and the vision system processor is arrangedto determine a surface shape of the object based upon the structuredlight pattern.
 19. The vision system as set forth in claim 18, furthercomprising, a second imaging system having a second image sensor and asecond optics having a second optical axis, the second optical axisbeing on-axis with a device optical axis adjacent to the object.